These are the cricitcal points. The only point seems to be at . This is in the given interval, so just find . If look at the value of the derivative just after , for example , it's clear that the point is a minimum. Google the "first derivative test" if you're not familiar with this.
Edit: the point I made is actually incorrect if you read string6bean1977's reply. I should have used the "Closed Interval Method." However, the point is still a minimum.